There is an increasing demand for portable electronic devices such as mobile phones with limited thickness and that are relatively dense. A back-lap and/or back-grinding process may be performed to reduce a thickness of a semiconductor device, which is one of main components of a portable electronic device. For example, the back-lap process may include a step of grinding or polishing a back surface of a wafer such as those not provided with any pattern. A final thickness of a wafer is typically determined primarily based on the type of semiconductor device or based on the needs of a particular customer.